fix #2362

Rather than removing all css now it will remove only css not listed in
the "relaxed" sanitize config.

app/logical/d_text.rb

@@ -321,7 +321,8 @@ class DText
         "a" => {
           "href" => ["http", "https", :relative]
         }
-      }
+      },
+      :css => Sanitize::Config::RELAXED[:css]
     )
   end
 end